The Internet Multicast Backbone ("MBone"), is a virtual network on the Internet, which has been in existence beginning as a research tool since the early 1990s. In the last few years, this same network has become more widely used as the medium for large scale live video broadcasts and their distribution to Internet subscribers. Additionally, Internet phone applications for PC platforms have spurred a tremendous increase in traffic and interest in the Internet for audio and video telephone applications.
It is a widely held belief that this medium has great potential for use by corporate Intranets as well as by private users. However, a major drawback with this medium is that groups of transmission signals, called packets, which in combination comprise the entire signal, are frequently lost by the medium, seriously degrading the video picture and sound quality, and making the medium currently unacceptable for expanding business applications.
To resolve this degradation problem, for example, in data applications, sophisticated retransmission based error recovery schemes have been previously proposed. However, unlike data transmissions which require 100% reliability in signal transmission, systems on the Internet can operate in virtual time allowing for signal error detection and correction without signal loss. One recent proposal for solving degradation in real-time multimedia transmission modifies the source and receiver applications to conform to a new protocol which then incorporates the retransmission of packets in the new protocol. Assembly and disassembly of video frames is done as part of the protocol. However, no request for retransmission is sent out if the current round trip delay is greater than an inter-frame period, which is assumed to be constant in this scheme. A major disadvantage is that the system requires frame level information and requires modification to the internal workings of the specific applications being used.
Accordingly, there is a need to provide a system and method which can retransmit lost packets without requiring any modifications of existing applications, sources and receivers.